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Mutations

Mutations. When something goes wrong…. Causes of Mutations. Mutations are caused by changes in the nucleotide sequence of DNA (A, T, C, G) or of a gene (specific area of a chromosome) This can occur: During DNA replication During cell division After cell division. Mutations Types.

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Mutations

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  1. Mutations When something goes wrong…

  2. Causes of Mutations • Mutations are caused by changes in the nucleotide sequence of DNA (A, T, C, G) or of a gene (specific area of a chromosome) • This can occur: • During DNA replication • During cell division • After cell division

  3. Mutations Types • Germ-Cell Mutations • Occur in an organism’s sex cells • Do not affect the organism itself but may be passed to offspring • Somatic-Cell Mutations • Take place in an organisms body cells and can affect the organism • Cannot be inherited • Lethal Mutations • Cause death, often before birth

  4. Gene Mutations

  5. Gene Mutations • Point mutations affect a single nucleotide • Base pair substitutions switches a nucleotide • Silent mutation • Does not change the amino acid • Missence mutation • Change of a single amino acid • Nonsense mutation • Changes amino acid to stop codon • Neutral mutation • Changes amino acid to chemical similar amino acid

  6. Gene Mutations • Frameshift Mutation • Change in reading frame due to adding or deleting a nucleotide AAT TGC CCG ACT TTT CGC CAT • Add A after 2nd nucleotide AAA TTG CCC GAC TTT TCG CCA T

  7. Chromosomal Mutations

  8. Chromosomal Mutations • These mutations can be detected by karyotyping • Nondisjunction • Homologous chromosomes or chromatids don’t split in division • Deletion • Loss of a piece of chromosome due to breakage • Duplication • Portion of the chromosome can be duplicated • Inversion • Part breaks off, then reattaches in reverse position • Translocation • Part breaks off, reattaches to a non-homologous chromosomes • Insertion • Extra DNA is inserted into a non-homologous chromosome

  9. Effects of Mutations • Always result in changes to genotype (DNA) but not always phenotype (what you see!) • Neutral • No effect • Beneficial • Enhances fitness • Deleterious • Decreases fitness

  10. Cystic Fibrosis

  11. Cystic Fibrosis • Genetic disorder affecting the respiratory and digestive system caused by defective gene on Chromosome 7 • 1000 different mutations in this gene have been identified • Most often caused by deletion of a single amino acid • Body produces a mucous that clogs the airways and increases risks of infection • Both parents must pass on the gene to their children • More than 10 million Americans carry the gene and don’t know it • About 2,500 babies are born with cystic fibrosis in the U.S. each year.

  12. Turner Syndrome

  13. Turner Syndrome • Caused by missing or incomplete X chromosome often due to non-disjunction • Women with Turner syndrome are usually sterile and cannot have children • Short in stature, stocky appearance, arms that turn out slightly at the elbow, receding jaw line, short webbed neck, and low hairline • Affects 60,000 females in the United States. This disorder is seen in 1 of every 2000 to 2500 babies born, with about 800 new cases diagnosed each year • In 75-80% of cases, the single X chromosome comes from the mother's egg; the father's sperm that fertilizes the egg is missing its sex chromosome

  14. Klinefelter Syndrome

  15. Klinefelter Syndrome • Caused by an extra X chromosome (XXY) in males due to by nondisjuction • Males are often tall and don’t develop secondary sex characteristics (facial hair, underarm hair, etc) • Often not diagnosed until puberty (less muscular body, more breast tissue, less hair) or when men try to have children due to sterility • Treated with hormone replacement therapy – testosterone injections • Klinefelter syndrome is one of the most common genetic abnormalities. It affects between 1 in 500 and 1 in 1,000 males.

  16. Sickle Cell Disease

  17. Sickle Cell Disease • Mutation on a gene on chromosome 11 that codes for the shape • Blood cells get stuck in the blood vessels and cannot transport oxygen, resulting in pain and damage to organs, leading to low red blood cell counts • Both parents must pas a defective gene to their children • Daily penicillin to prevent infections, folic acid to build new cells, blood transfusions, bone marrow transplant • Unlike normal red blood cells, which can live for 120 days, sickle-shaped cells live only 10 to 20 days. • In the United States, the disease most commonly affects African-Americans. About 1 out of every 500 African-American babies born in the United States has sickle cell anemia

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